You are responsible for payment of any taxes that were assessed during the time you were the owner up until the closing date. Any amount due should have been prorated as of the closing date. Your post says you sold in Maine (which I assume is where the unpaid tax issue lies) but then you mention a lien on property in the Villages. Liens for unpaid taxes follow the property and cannot be transferred to other property especially property in another state. I assume you did sign a document that said something close to inadvertent errors happen but you will take steps to correct them. It is a processor or closing agent's nightmare when errors occur and they have to reach out after a closing to either collect additional funds or have documents re-signed. You should ask the closing agent or whoever is requesting funds what the time period is that is due and also make sure that you were given credit (pro-ration) for days you were not the owner. A prior post mentioned title insurance - title insurance only insures any defects in the title and the chain of ownership - this will not apply in this matter. It is an unfortunate oversight or omission. You don't need to contact any attorney - just deal with the title company (In Maine a lot of law firms act as closing agents) or law office and make sure you understand the amount you are being asked to pay. My source of this information - I have been a paralegal in Maine since 1984 and have handled close to 3000 closings (I later was a foreclosure paralegal and foreclosed on the people I helped close). I hate to admit it but I have actually had to make these types of calls myself. Please let me know if I can explain myself further. Signed - a Mainer now but headed to my beloved home in Monarch Grove by January 1, 2021!

Title insurance
 

Read the policy. If it doesn't cover this then what is it for?

Title Insurance does not protect the seller in a real estate transaction. It protects the BUYER, and coincidentally the Lender if there is one. Since the attorney / title agent missed it he may have to pay it to make the buyer whole, but he has full legal rights to pursue the seller for reimbursement.

Subrogation Definition

I don't think title insurance applies at all in this situation. The closing attorney made a calculation error and notified the seller in a timely manner. The seller owes the property tax. I may agree that title insuance may apply if this error was not discovered until several years later, but that is not the case.

What a question? Most people pay their debts.

A good friend (former bank president) told me it's a very simple process to get a lien on property.

The HONORABLE thing to do is pay the taxes!

The title company will be on the hook for the unpaid tax. I would call their bluff, but that's me. If you're the type who likes pushing limits, which sounds like you are, go for it.
But your question is, are you "legally" obligated to pay the tax.The answer is a simple no. Not your house any longer, legally you owe nothing.

You know you owe the taxes, so why pay an attorney just be cause you want him to say No you don't have to pay. That isn't going to happen and you will be paying twice...once for the tax and 2nd for the snag in your character which lowers your self-esteem.

The title company’s job is to insure you that you are getting clear title. They missed those outstanding taxes. That’s what title “insurance “ is. They will fight you, but they need to play that bill.

Why
 

Why would you ask us? You’ll just get 20 different answers. I guess then you can pick out the one you like the most. Hmm...

Actually, the OP doesn't owe any taxes, the tax has been paid.The title company is claiming he owes a debt to them as a result of their incompetence, nothing more. They erred, not the OP's fault. Unless contractually the OP is responsible for a title company error he owes nothing.
If this came to a judicial decision, it would benefit the defendant.

If there are taxes owed at the time of sale, would seem that the responsibility for payment would be determined at the time of sale by who gets the benefit. If taxes for the future, then the new buyer. If for the past, then the seller. If split simply divide.

Like I always say "If you think you own your home, don't pay the taxes on it and see who REALLY owns it".

Based upon my experiences having bought and sold numerous homes in the past forty years title insurance comes in two types of policies. The first one generally protects the bank/mortgage company from defects in the title. The second policy which can be purchased from the closing attorney protects the buyer. I am unaware of a title insurance policy that protects the seller(s).

If you were the seller in this transaction and there is nothing is the sales contract/agreement that says someone else is responsible for the back taxes then you would be responsible to pay the pro rata share of the taxes up to the day the property was transferred. If you go ahead and pay now you could save additional potential costs which could be assessed for interest and late fees. Rest assured if this matter falls back in the hands of the title insurance company and they end up paying it will not be long before you are contacted to reimburse them for this expense including applicable attorney fees. As many before me have already said, do the right thing and quit trying to get away with not paying what you rightfully owe.

Wrong.